The price comparisons between the Gen90 and EC1 are a bit of a joke. It's like comparing apples and oranges!
Both will control the engine as the OP requires (like the above are both fruits), but beyond that you're not comparing like for like.
The Gen90 will run a standard 172/182 on its own, allowing the owner to retain dash functionality such as fuel consumption, and the ESP light stays off, plus the one touch windows work,etc. The EC1 cannot retain all this functionality on a standard car without the standard ECU remaining in place!
If you're after a direct price comparison for the end result of running a car and retaining all the functionality, then compare the price of a Gen90, with that of a wired in EC1 (let's ignore the cost of mapping either ECU just at the moment) plus the cost of the standard ECU (as without that it cannot achieve the stated functionality). That is a like for like comparison.